In 1923, T S Eliot wrote that the critic must have “a very highly developed sense of fact”. This is also a useful attribute for the historical novelist but it is precisely what is missing from Therese Anne Fowler’s fictional account of the life of Zelda Fitzgerald, which is less a fiction than a series of falsities.

Fowler’s novel retells the story of Scott and Zelda Fitzgerald, from their courtship in Montgomery, Alabama at the end of the First World War, through Scott’s sudden fame as the bestselling author of This Side of Paradise in 1920 and their marriage a week later. The Fitzgeralds proceeded to take America by storm, while their well-publicised escapades in the early 1920s helped to inspire The Great Gatsby. After it was published in 1925 to disappointing sales and mostly uncomprehending reviews, the fun began to spiral into something more destructive. Fitzgerald’s drinking raged out of control and Zelda’s behaviour, always unpredictable, started to become seriously erratic.

In 1930, Zelda had a mental breakdown, and was hospitalised. She spent the next decade in and out of psychiatric clinics, while Fitzgerald’s alcoholism took a stranglehold over his life. Recriminations were thrown, Zelda’s friends and family murmuring that Scott was to blame – he had driven her crazy, or else was a jazz-age Mr Rochester locking up an inconvenient Bertha Mason. In fact, there is a great deal of epistolary evidence to show that Fitzgerald was desperate to find a cure for the woman he loved until he died suddenly of a heart attack in 1940.

Zelda was in and out of hospital for the next eight years but conspiracy theories are nothing if not resourceful: and so we are told that it was the treatments to which she was subjected that drove Zelda mad. It’s a tiresome story but tenacious, and unfortunately one to which Fowler whole-heartedly subscribes – the kind of victim feminism that can only see women as casualties and martyrs of selfish, domineering men, rather than as agents of their own destinies.

The truth, evident from the accounts of virtually everyone who knew them and from their own writings, is that both Scott and Zelda were brilliant, beautiful, charming, egotistical, theatrical, impetuous and selfdestructive; and they loved each other deeply, to the ends of their lives. “We ruined ourselves – I have never honestly thought that we ruined each other,” Scott wrote to Zelda soon after her breakdown. But Fowler knows better.

The emphasis in Z, an afterword tells us, “is not on factual minutiae but rather on the emotional journey of the characters”. Fowler certainly pays little attention to facts: names are wrong throughout (Tallulah Bankhead was called “Dutch”, not “Tallu”; Edna St Vincent Millay was “Vincent”, not “Edna”; Alexander Woollcott was “Alec”, not “Alexander”), as are easily checked dates (Fitzgerald’s play The Vegetable flopped in November 1923, not 1922). Relationships are rewritten: Fitzgerald quarrelled with Alec McKaig in March 1922, ending the friendship, so the Fitzgeralds should not be meeting “our beloved Alec McKaig” in Paris in 1925. The Black Bottom was not later “called” the Charleston; they are two different dances. Anachronistic language abounds: people in the 1920s did not say “come on” or “when he does shit like that”.

Defending such errors as the poetic license of the novelist is a prevarication: sloppiness is not art. Historical fiction can imaginatively fill gaps in historical knowledge, bringing the past intimately to life, or it can rewrite history, as a counterfactual. It’s not clear what virtue there might be to getting the known facts wrong, however, and most of what Fowler invents goes against the letter or the spirit of what we do know.

This is true not only in the case of factual “minutiae” but also in terms of the larger emotional lives of the characters that Fowler claims concerned her more. It is precisely Zelda’s character that Fowler fails to respect or to capture, turning one of the most memorable women of her era into a sanctimonious bore, with decidedly 21st-century attitudes to monogamy, work, alcohol and child-rearing. Fowler’s Zelda is driven to exhibitionistic behaviour only by “the need to take some kind of action, even if it was wrong”, once tossing her lace knickers on to a lunch table.

The real Zelda was famous for throwing off her clothes at the drop of a hat, for dancing on tabletops and necking with men at parties, inviting them to take baths with her and reportedly chasing the 16-year-old brother of one party host up the stairs, none of which appears in Fowler’s account. Nor was there ever any suggestion that she regarded such antics as “wrong”. Indeed, conventional moralising was anathema to Zelda. It is simply absurd to suggest, as Fowler does, that Zelda would have been shocked to hear that Scott got drunk and “exposed himself” at a party. The real Zelda would be insulted at being portrayed as a prim Victorian maiden.

Fowler’s Zelda keeps preaching moderation and prudence in a way that would have made the historical Zelda hoot with laughter. She urges Scott to spend less and drink less. But Zelda’s own letters at the time admit with casual insouciance how much she’s been drinking, what she’s been buying, how much fun they’ve been having, very rarely mention their small daughter (who is, naturally, a subject of proper maternal devotion in Fowler’s banal imaginings) and never assert the need for temperance until after her breakdown.

On the contrary – in the summer of 1923, she wrote to a friend complaining that Scott had started on his novel and had retired into a monastic life, which Zelda was finding very boring. Fowler’s Zelda is horrified when Scott contemplates working on Gatsby after he’s had a drink; the historical Zelda embarked on an affair while Scott was working on his masterpiece because she was bored.

Needless to say, Fowler also thinks that Zelda was the artist in the family. Scott begins as a cynical self-publicist, and ends a sodden mess. It’s amazing that the unpleasant cretin in these pages could produce anything, much less The Great Gatsby. But happily he had Zelda’s constant, wifely support. Zelda comes up with the title for Gatsby and helps Scott write The Vegetable (an unfortunate credit for a champion of Zelda to offer, given that the play was Fitzgerald’s greatest professional failure).

Fowler can’t even grant that Scott was the one who kept a ledger; Zelda does that too. Even more ironically, although apparently convinced that Zelda was the greater writer, Fowler entirely fails to evoke her remarkable, imagistic voice. Zelda wrote in her autobiographical novel, Save Me the Waltz: “Possessing a rapacious, engulfing ego their particular genius swallowed their world in its swift undertow and washed its cadavers out to sea. New York is a good place to be on the upgrade.”Fowler’s Zelda thinks: “The building was a wonder. Everything in New York City was a wonder, including Scott, who was treating me like the princess I’d once imagined I was.”

Writers of historical novels owe a debt to the facts that have inspired their fictions: Fowler wants to capitalise on the facts but feels no obligation to them. Where there is so little fidelity to the known facts, there can be no meaningful notion of history, no imaginative supplementing of incomplete stories, and the “minutiae” about which Fowler is so dismissive cannot be transcended. Certainly no sense of truth, history or fiction can flourish in a space that has no sense of fact.

Sarah Churchwell’s “Careless People: Murder, Mayhem and the Invention of The Great Gatsby” is published by Little, Brown on 6 June